1. Field of the Invention
The present invention concerns a method of degreasing and cleaning an object deposited with oils, as well as an apparatus used therefor. The present invention more particularly concerns such a method and apparatus which can be suitably utilized, for example, as a precleaning in a heat treatment step or as an intermediate cleaning after a hardening step.
2. Description of the Prior Art
As examples of degreasing and cleaning methods which have been applied to metal materials deposited with oils, the following are known:
(1) Alkali cleaning: where cleaning is achieved by dipping the material into a warm aqueous solution or alcohol solution of sodium hydroxide or other alkali agent; or by spraying such a solution; alkali cleaning is applied to heavy oil contamination.
(2) Cleaning with a surface active agent: where cleaning is achieved by dipping the material into a warm aqueous solution of a surface active agent, or by spraying such a solution. Surface active agent cleaning is applied to slight deposition contamination or oil membranes.
(3) Cleaning with chloro-solvent: which involves dipping or vapor cleaning by using a chloro-solvent, such as, for example, 1,1,1-tri-chloroethane, trichloroethylene and perchloroethylene.
(4) Cleaning with a fluoro-solvent: which involves dipping or vapor cleaning, such as, for example, by using Freon 113.
However, degreasing and cleaning methods (1) and (2) using the alkali agent or the surface active agent are not generally employed since they involve problems. For example, cleaning performance is poor and quite often causes stains on the surface of an object to be cleaned. Likewise, liquid waste treatment is expensive.
On the other hand, degreasing and cleaning methods (3) and (4) using chloro-solvents or fluoro-solvents have high cleaning performance. However, the chloro-solvents involve problems since they show strong toxicity and evaporate greatly. Moreover, the chloro-solvents scatter from cleaning apparatus or treated objects owing to their volatility and thereby contaminate underground water as carcinogenic substances. Accordingly, legal regulations for their use have become more severe in recent years. Use of the fluoro-solvents has also been extremely restricted since they form ozone layer destructive substances when released to the atmosphere.
3. Object of the Invention
In view of the above, the present invention has been accomplished taking notice of the foregoing problems in the prior art. Therefore, it is an object hereof to provide a metal degreasing and cleaning method using neither alkali agent nor chloro- or fluoro-solvent which would result in public pollution or circumstantial contamination, as well as an apparatus used for the method.